The purpose of this Program Project grant is to support the following proposed research protocols: 1. The effect of mannitol on nephron function hypoperfusion. 2. Intrarenal distribution of filtration and blood flow in relation of sodium excretion. 3. Extrarenal adaptation to potassium in man. 4. The effect of bile acids on renal function. 5. Renal compensatory growth. 6. Some aspects of potassium depletion in man.